Miss Marple is wonderful. After Poirot, it is so refreshing to have a hero that is self-effacing.
I also enjoy how the story is narrated by Rev Clement, an elderly clergyman with a young attractive wife. The implicit authority of a COE priest; the slight insecurity of someone marrying a woman 20 years his junior; the gentle self-deprecation of a sensible clergyman; everything is done exactly right.